This invention relates to a unitized automobile body construction, sometimes called a unibody, and more particularly to a front compartment which is readily removable and replaceable to facilitate repair of collision damage.
Automobiles were originally made with separate body and frames spring-mounted onto front and rear axle assemblies.
Beginning about 20 years ago in Europe, and more recently in the United States, automobile manufacturers adopted the unibody style which uses a one piece lightweight steel structure instead of the traditional separate frame and body. Among the advantages are reduced first cost, more usable passenger room, a smaller body, and lighter weight which greatly improves fuel economy. American manufacturers have switched over more than 80% of their production to unibodies.
Aside from these advantages, the unibodies have a serious drawback in that repair of collision damage is much more difficult and expensive resulting in higher maintenance and insurance costs. The great majority of accidents result in damage to the front and of at least one of the cars involved. Inasmuch as the inner side panels of the front compartment are integral with the rest of the body and they provide primary structural support for the engine, front wheels and steering mechanism, a substantial number of collisions result in total loss of the car because the cost of refabricating the front end with the precision needed for safe operation is too high to be practicable.
The unibody structure actually supports the weight of the car. If it is only fractionally out of alignment, it can be undrivable or unsafe. Without a chassis, the unibody skin must be so precise that there is only about a 3-millimeter margin for error in supporting the wheel and steering components. Serious collision damage involving distortion of the inner side panels along the front or engine compartment can be corrected only by the use of jigs, and elaborate and expensive measuring devices, precision support benches, and heavy-duty power bending equipment.
The pieces of steel that make up the unibody are progressively overlapped and welded, sometimes by several feet, in manufacture and the welded joints are covered or inaccessible in the final assembly. Repairing or replacing one section may require dismantling several sections, pushing costs up.
A practice called "clipping" is used for repairing seriously-damaged unibody cars. This entails combining a good rear end from one car with a good front end from another, but this is far from satisfactory because it is economically impracticable to weld the two halves together and produce an assembly duplicating factory integrity and specifications.
As a further complication, the automobile industry now uses light gauge steel that cannot tolerate the intense welding heat as well as the heavier gauge steel used in older cars. Many repairs on unibody cars are merely cosmetic, it being impracticable to duplicate the original strength of the assembled parts.
Car owners are paying for this in two ways: increasing insurance premiums; and increasing numbers of cars which are declared total losses; all of which results in higher overall costs to the public generally.